Red-lion TCU User Manual download pdf (Page 77)

As shown in the Auto-Tune Operation Figure 40, Auto-Tune cycles the

process at a control point 3/4 o f the distance between the current process

temperature (at the instant Auto-Tune is started) and the temperature

setpoint. The 3/4 control point was selected to reduce the chance of

temperature overshoot at setpoint when Auto-Tuning at start-up. If

Auto-Tuning from setpoint and temperature overshoot is unacceptable,

temporarily lower the setpoint by an amount of the temperature oscillation

and then Auto-Tune. Reset the setpoint to the original value when Auto-Tune

is complete. After starting Auto-Tune, the secondary display indicates the

current phase (Aut1, Aut2, Aut3, & Aut4). If the controller remains in an

Auto-Tune phase unusually long, the process or connections may be f aulty.

Additionally, during Auto-Tune it is important that disturbances to the

system be minimized, as these may have an effect on the parameter

determination.

Initiate Auto-Tune

Auto-Tune may be initiated at start-up, from setpoint, or at any other

process temperature point.

To Initiate Auto-Tune:

1. Make sure that Auto-Tuning is enabled in parameter lockouts module.

2. Place the controller into the normal display mode.

3. Press PAR for 3 seconds from normal display mode.

4. Scroll to “tUNE” by use of PAR, if necessary.

5. Select “YES” and press PAR.

Auto-Tune is initiated.

To Cancel Auto-Tune: (Old PID settings remain in effect).

A) Make sure that Auto-Tuning is enabled in parameter lockouts module.

1. Place the controller into the normal display mode.

2. Press PAR for 3 seconds from normal display mode.

3. Scroll to “tUNE” by use of PAR, if necessary.

4. Select “ NO” and press PAR.

5. Auto-Tune canceled.

B) Or reset the controller by disconnecting AC power.

Note: If using the linear DC output for control, full power is applied (+100%

OP1 or -100% OP2) regardless of the output power limit settings. Set the

Linear DC Output scaling points to limit the magnitude of the output, if

desired.

Auto-Tune Of Heat/Cool Systems

During Auto-Tune of heat/cool systems, the controller switches the

cooling output (OP2) on and off in addition to the heat output (OP1). The

heat/cool deadband parameter (db-2) determines the amount of overlap or

deadband between the two outputs during Auto-Tune. Refer to ON/OFF

CONTROL, page 66, for the operation o f this parameter. The heat/cool

deadband parameter remains unchanged after Auto-Tune is complete.

Therefore, when proportional control is started after the completion of

Auto-Tune, this parameter may need to be reset.

It is important that external load disturbances be minimized, and if present,

other zone controllers idled as these may have an effect on the PID constant

determination. The controller additionally sets the Relative Cooling Gain

parameter (GAN2) for heat/cool systems.

Auto-Tune Of Internal Cascade Controllers

Auto-Tune of Internal Cascade controllers involves tuning of the Primary

PID and Secondary PID parameters. Each set of parameters is tuned

individually with the secondary parameters normally tuned first. For Internal

Cascade controllers, Auto-Tune offers the option of tuning the Primary or

Secondary:

tunE

no - No Auto-Tune or abort Auto-Tune

PRI - Start Auto-Tune of primary or Auto-Tune of primaryin progress

SEC - Start Auto-Tune of secondary or Auto-Tune of secondary in

progress

The Auto-Tune status display indicates the set of parameters actively

Auto-Tuned:

Tune

Phase

Display

(Primary)

Display

(Secondary)

1 APr1 ASC1

2 APr2 ASC2

3 APr3 ASC3

4 APr4 ASC4

1 2 ... 72 73 74 75 76 77 78 79 80 81 82 ... 103 104

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Red-lion TCU User Manual Page 77

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